Dear people who post things like "Incest is neat" and "Whites are smarter than blacks": those things are currently controversial. Therefore, they don't come close to being unthinkable or impossible to talk about.

Nitpick: men dominating women and fathers (not mothers) deciding infanticide are not features of the ancestral environment, they come from the invention of agriculture, moving out of the ancestral environment.

Now, "agriculture was a mistake, let's go back to hunting, gathering, and killing babies born during famines", that's more of a sacred cow^W wild aurochs.

Other not-easily-thinkable positions (I don't believe any of these, but believe they're not utterly ridiculous):

• Radfems are righter than they know; it is unethical to do anything to anyone (such as looking at them or talking to them) without explicit consent.
• Vertebrates are people. There should be systems to extract their preferences so they can vote and debate. Letting your goldfish die is murder.
• The above also applies to the overwhelming majority of animals, and maybe some plants, fungi, and other living or not things (e.g. cancer is a person). Stepping on a anthill is mass slaughter. (I used to believe a version of this as a kid.)
• It's impossible to predictably improve any complex system, let alone a whole country. Anyone pushing for a policy is flailing wildly in the dark. Successes like Atatürk were the product of blind luck and historians with a bad case of narrative fallacy.
• Personal identity changing over time counts as death. It's better to kill people, so they die once, than allow them to live, so they die creating another doomed person.
• "<foobar> is ruining our intelligence!" claims are all true. If we'd shunned writing, progress would have been slower and bad at trickling down but ultimately much greater.